The main circuit breaker on the low-voltage side trips frequently
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When the factory was built, Changshu low-voltage circuit breakers of the CW1-4000 type were used. Within less than a year of operation, the main circuit breaker on the low-voltage side would frequently trip. If there was a problem with the load side, it should be the circuit breaker at the next lower level that would trip, so why does the main breaker trip directly instead? I contacted the manufacturer, and they said it was a problem with the under-voltage release mechanism of the main low-voltage circuit breaker. However, even after replacing the release mechanism, the issue persisted over time. The high-voltage side continued to supply power, so it couldn’t be under-voltage that caused the circuit breaker to trip. I hope experts can help figure out where the problem lies. Thank you very much! ! ! ! !
Lock the under-voltage mechanism in place, to prevent the under-voltage coil from being affected. Even though power is supplied on the high-voltage side, there may still be voltage fluctuations, such as those that occur during thunderstorms or when large motors start up. Check to ensure that there is no instantaneous power cut protection in place, and also examine the settings for grounding protection
Could an alarm device be installed at the upstream side of the main circuit breaker (on the low-voltage side of the transformer)? This way, if there are sudden voltage fluctuations in the high voltage side, an alarm can be triggered!
You can add an under-voltage relay to generate a holding signal. It’s not quite clear how tripping occurs; is the trip coil of the thermal or magnetic type? Are the harmonics severe? If the under-voltage mechanism is locked in place yet tripping still happens without any reason, it’s likely there’s a problem with the circuit breaker’s own mechanism – consider replacing it
Thank you! Yes, I really don’t know what’s causing the frequent tripping. Would locking the under-voltage release device have any negative effects on the entire system? As you suggested, should the under-voltage relay be installed on the low-voltage side of the transformer? Is the purpose to see whether sudden fluctuations in high voltage send a signal to the under-voltage relay, so that it can be determined whether the problem lies with the high voltage or with the circuit breaker itself?
Important equipment must not use domestic brands; Schneider and ABB are the choices to go with
Jumping from the next-level switch to the main switch indicates that a high current is flowing in one of the branch circuits on the low-voltage side. The reasons for this high current are as follows: first, there may be a short-circuit fault in one of the branch circuits; second, when a large motor starts, the branch switch does not trip while the main switch does. It’s possible that there is an issue with the setting of the quick-break threshold for your main switch. When analyzing a problem, it is necessary to do so in a thorough and detailed manner. Without going to the site for a comprehensive inspection, it is difficult to arrive at a definite conclusion. This suggestion is provided for reference only; I hope it can help you.
A current trip surely isn’t without reason; there must be a signal light
There must be a reason for something to happen without any apparent cause. Have you seen the circuit board of the under-voltage trip device? It’s likely that the CPU has failed